In the logistics systems field as well as in person and goods monitoring applications it is necessary to locate the position of objects and/or individuals. Wireless communication devices can be used for this purpose, said devices being attached to the objects whose position is to be located and communicating wirelessly with further units via a radio module. When necessary, the positions of the objects can then be determined by way of the wirelessly transmitted communication signals. In a WLAN network, for example, the position of the communication device can be detected by way of the field strength of the radio link relative to access points of the network and from this the location of the device can be estimated. Another possible wireless connection for determining the location of a device are mobile radio links and GPS, wherein satellite signals are received via a GPS antenna and the position is calculated from this.
Conventional wireless communication devices have the disadvantage that the radio modules used in the devices have a relatively high transmit power of 100 mW to 2000 mW. Due to this high energy consumption the operation time of devices of this kind is short, in particular in the case of mobile applications, since said devices are often provided with batteries which quickly become discharged due to the high transmit powers.
In the case of trackable wireless communication devices it is known from the prior art to reduce the power requirements by means of a short turn-on time of the energy-intensive radio module and of the processor in the device. However, it proves disadvantageous that abrupt and rapid changes in the position of said devices are not tracked sufficiently quickly, since under certain conditions such changes of position occur when the radio module is switched off and consequently are not detected.